Reagent refill and supply system for an SCR exhaust aftertreatment system

ABSTRACT

An internal combustion engine includes an exhaust manifold, and a selective catalytic reduction exhaust aftertreatment system. The selective catalytic reduction exhaust aftertreatment system includes a reduction catalytic converter in communication with the exhaust manifold; a reagent holding tank in fluid communication with the reduction catalytic converter; and a reagent supply canister selectively and removably couplable with the reagent holding tank.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to exhaust aftertreatment systems for usein internal combustion engines, and, more particularly, to such exhaustaftertreatment systems using selective catalytic reduction.

2. Description of the Related Art

Increasingly stringent emissions control standards necessitatecontinually improved emissions from internal combustion (IC) enginesused as motive power for vehicles. At present, the most significant ofthese emissions are sulfur dioxide (SO₂), oxides of nitrogen (NOx), andairborne particulate.

NOx refers to the cumulative emissions of nitric oxide (NO), nitrogendioxide (NO₂) and trace quantities of other species generated duringcombustion. NOx emissions are minimized using low NOx combustiontechnology and postcombustion techniques. If combustion modificationsalone are insufficient, postcombustion techniques such as selectivecatalytic reduction (SCR) systems may be employed. In SCR systems, NOxis reduced to nitrogen (N₂) and water (H₂O) through a series ofreactions with a chemical reactive agent (reagent) injected into theexhaust gas. Ammonia and urea are the most commonly used chemicalreagents with SCR systems.

In 2007, it is estimated that engine out NOx emissions will on averagebe approximately 1.2 g/hp-hr (gallons/horse power-hour). In order tomeet the 2010 NOx standard of 0.2 g/hp-hr, an SCR system (using ammonia)can be used. For about 1 g/hp-hr NOx reduction the amount of ammonia(NH₃) required is not very large. Since anhydrous ammonia is a toxicsubstance, another likely reagent is an aqueous solution of 32.5% ureaand 67.5% water, although the exact reagent formulation can vary fromone application to another. To achieve the desired 1 g/hp-hr NOxreduction, the amount of the proposed reagent required is approximately1.3% of the diesel fuel burned, on average.

Since the urea mixture is a depletable supply, one contemplated supplysolution is to provide a bulk tank at fueling stations with a supplyhose and nozzle used for refilling a holding tank on the vehicle. Thisurea mixture supply solution may have logistics difficulties, however,with inadvertent spillage from the nozzle, the need to dedicate orretrofit a supply hose and nozzle at each fueling island, etc.

What is needed in the art is a quick, convenient and relatively safesystem and method for refilling a reagent for use in an SCR exhaustaftertreatment system.

SUMMARY OF THE INVENTION

The present invention provides a reagent refill and supply system andmethod including a reagent holding tank permanently onboard the vehicle,and a portable and selectively couplable reagent supply canister forrefilling the reagent holding tank.

The invention comprises, in one form thereof, an internal combustionengine including an exhaust manifold; and a selective catalyticreduction exhaust aftertreatment system. The selective catalyticreduction exhaust aftertreatment system includes a reduction catalyticconverter in communication with the exhaust manifold; a reagent holdingtank in fluid communication with the reduction catalytic converter; anda reagent supply canister selectively and removably couplable with thereagent holding tank.

The invention comprises, in another form thereof, a method of operatingan internal combustion engine, including the steps of: treating exhaustgas with a selective catalytic reduction system including a reductioncatalytic converter; supplying a reagent to the reduction catalyticconverter from a reagent holding tank; coupling a reagent supplycanister with a refill head on the reagent holding tank; and refillingthe reagent holding tank with reagent from the reagent supply canister.

An advantage of the present invention is that the reagent can be quicklyand easily replenished in a motor vehicle at periodic intervals as it isdepleted from the reagent holding tank.

Another advantage is that the periodic interval can be a predeterminedinterval or can be a varying interval based upon a sensed reagent levelin the holding tank.

Yet another advantage is that the reagent supply canister is sealed tothe ambient environment and automatically opened upon coupling with thereagent holding tank to allow reagent refilling.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a schematic illustration of an internal combustion engineincluding an embodiment of a reagent refill and supply system of thepresent invention;

FIG. 2 is a plan view of the reagent refill and supply system shown inFIG. 1, with the reagent supply canister removed from the reagentholding tank;

FIG. 3 is a plan view of the reagent refill and supply system shown inFIGS. 1 and 2, with the reagent supply canister coupled with the reagentholding tank;

FIG. 4 is a plan view of another embodiment of a reagent refill andsupply system of the present invention, with one reagent supply canistercoupled with the reagent holding tank, and a reserve reagent supplycanister carried in a standby position.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate one preferred embodiment of the invention, in one form, andsuch exemplifications are not to be construed as limiting the scope ofthe invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, there isshown an IC engine 10 including an embodiment of an SCR exhaustaftertreatment 12. In the embodiment shown, IC engine 10 is a dieselengine including a cylinder block 14 defining a plurality of combustioncylinders 16, an intake manifold 18, an exhaust manifold 20 and aturbocharger 22.

Cylinder block 14 is shown as including six combustion cylinders, butmay also include a different number of combustion cylinders, such aseight, ten or twelve combustion cylinders.

Intake manifold 18 and exhaust manifold 20 are each in fluidcommunication with the plurality of combustion cylinders 16, and may beof single part design, as shown, or of multiple part design.

Exhaust manifold 20 discharges exhaust gas to turbine 24 of turbocharger22. Turbine 24 may be of a fixed geometry as shown, or may be anadjustable turbine such as a variable geometry turbine (VGT). Exhaustgas from exhaust manifold 20 rotatably drives turbine 24, and is thendischarged to SCR exhaust aftertreatment system 12, as will be describedin more detail hereinafter.

Turbine 24 rotatably drives compressor 26 via a shaft 28, as indicatedby arrow 30. Compressor 26 receives air from the ambient environment,compresses the air and provides compressed charge air to intake manifold18.

SCR exhaust aftertreatment system 12 generally includes a reductioncatalytic converter 32, doser 34, reagent holding tank 36 and reagentsupply canister 38. Reduction catalytic converter 32 may be ofconventional design for an SCR exhaust aftertreatment system. Doser 34provides a predetermined amount of reagent which is mixed with theexhaust gas discharged from turbine 24. The reagent is preferably mixedwith the exhaust gas upstream from reduction catalytic converter 32 forsufficient mixing prior to entering reduction catalytic converter 32.Doser 34 may also be of any suitable configuration, and is thus notdiscussed further.

Reagent holding tank 36 and reagent supply canister 38 together define areagent refill and supply system 40, shown in more detail in FIGS. 2 and3. Reagent supply canister 38 is selectively and removably coupled withreagent holding tank 36 for selectively filling reagent holding tank 36at periodic intervals. Reagent supply canister 38 is shown in anuncoupled position above reagent holding tank 36 in FIG. 2, and is shownin a coupled position in FIG. 3.

Reagent holding tank 36 includes a refill head 42 which is sized andconfigured to couple in a sealed manner with reagent supply canister 38.More particularly, reagent supply canister 38 includes a nozzle 44having an outside diameter which is slightly smaller than the insidediameter of refill head 42. Refill head 42 includes an annular groove(not numbered) at the inside diameter thereof which receives an O-ringseal 46. O-ring seal 46 fluidly seals between nozzle 44 and refill head42 when reagent supply canister 38 is coupled with reagent holding tank36 (FIG. 3).

Refill head 42 includes a first latch 48 and nozzle 44 includes a secondlatch 50 which mate together when reagent supply canister 38 is coupledwith reagent holding tank 36. In the embodiment shown, latches 48 and 50are bayonet latches, but may be differently configured depending uponthe application. Latch 48 is a female-type bayonet latch and latch 50 isa male-type bayonet latch.

Positioned within nozzle 44 is a spring biased valve 52 which opens andcloses to substantially seal reagent supply canister 38 from the ambientenvironment when in a closed position, and allow transfer of the reagentfrom reagent supply canister 38 to reagent holding tank 36 when in anopen position. In the embodiment shown, valve 52 is in the form of avalve disk which is biased to the closed position by a compressionspring 54. Valve 52 is shown in the closed position in FIG. 2.

To bias valve 52 to an open position shown in FIG. 3, reagent holdingtank 36 includes a valve opener pin 56 having a distal end which isgenerally centrally positioned within refill head 42 and extends towardthe opening of refill head 42. When reagent supply canister 38 iscoupled with reagent holding tank 36, valve opener pin 56 opens valvedisk 52 by exerting a force against valve disk 52 and compressing spring54.

Reagent holding tank 36 may also include an optional heater 58 thereinfor heating the reagent during cold weather. In the embodiment shown,heater 58 is in the form of a single resistance heater wire configuredas a heater coil extending into a sump 60 in the bottom of reagentholding tank 36. A suction line 62 in communication with doser 34 has aninlet 64 for receiving reagent near the bottom of sump 60. Heater 58receives electrical power at electrical leads 66 from an on-board powersupply (such as one or more vehicle batteries) through controllableactuation using onboard controller 68.

To provide an operator with an indication of the level of reagent withinreagent holding tank 36, one or more reagent level sensors 70 arepositioned at respective heights within reagent holding tank 36. In theembodiment shown, a pair of reagent level sensors 70 are incommunication with controller 68 via respective leads 72. Controller 68receives a signal from one or more reagent level sensors 70 and providesan output signal to visual indicator 74 providing an operator with areal time indication of the reagent level within reagent holding tank 36and/or the need to refill reagent holding tank 36.

SCR exhaust aftertreatment system 12 may also optionally include areagent quality sensor 76 providing an output signal to controller 68indicative of the quality of reagent within reagent holding tank 36.Additionally, an optional NOx sensor 78 (FIG. 1) also coupled withcontroller 68 may be positioned in the exhaust gas flow downstream fromreduction catalytic converter 32.

Referring now to FIG. 4, another embodiment of a reagent refill andsupply system 80 of the present invention is shown. Reagent refill andsupply system 80 includes a reagent holding tank 82 and a reagent supplycanister 84A which are similar in many respects to reagent holding tank36 and reagent supply canister 38 shown in FIGS. 1-3. However, reagentholding tank 82 does not include a sump, includes only a single reagentlevel sensor 70, and does not include a bayonet type latch. Rather, apair of finger type latches 86 on opposite sides of reagent supplycanister 84A engage the upper surface of an annular ring 88 at the outerperiphery of reagent supply canister 84A. An onboard reserve canisterholder 90 carries a reserve reagent supply canister 84B which may beused for refilling reagent within reagent holding tank 82. Reservereagent supply canister 84B is biased in an upward direction by acompression spring 92, which is compressed to a greater or lesser extentdepending upon the amount of reagent within reserve agent supplycanister 84B. A canister weight sensor 94 coupled with controller 68provides a signal indicating the amount of reagent within reservereagent supply canister 84B. It may be possible to configure canisterweight sensor 94 as a proximity sensor, inductive sensor or othersuitably configured sensor, depending upon the application.

Reagent refill and supply system 80 also includes an optional housing 96in which reagent holding tank 82, reagent supply canister 84A andreserve reagent supply canister 84B are positioned. Of course, it isalso possible to enclose reagent refill and supply system 40 shown inFIGS. 2 and 3 within a housing.

During operation, when the level of the urea solution reaches the upperreagent level sensor 70, a light in the instrument panel indicates thatat the next diesel fueling the urea solution needs to be replenish withone canister of urea. In the case that the driver, for some reason,fully refueled the diesel tank(s) just before the upper reagent levelsensor 70 sent the signal, there is enough urea solution between theupper reagent level sensor 70 and the lower reagent level sensor 70 foran uninterrupted trip achievable with full tanks of the diesel fuel. Inthe case of 200 gallons of diesel fuel, that would be about 2.6 gallonsof urea solution. If for some reason, the driver would again fail torefill the urea, then during the next trip when the level of the reagentreaches the lower reagent level sensor 70, a red light on the instrumentpanel indicates that the reagent must be refilled soon. The volume ofthe urea below the lower reagent level sensor 70 (approximately 0.4gallons) is sufficient for approximately 240 miles of travel. At thattime reagent holding tank 36 must be filled with 6 gallons of urea (tworeagent supply canisters 38).

During a regular diesel refueling, the operator purchases one reagentsupply canister 38 (or two if required). After an optional cap (notshown)is removed, reagent supply canister 38 is placed on refill head42. O-ring seal 46 engages with nozzle 44, and after lowering of reagentsupply canister 38, bayonet type latches 48 and 50 are latched togetherby turning reagent supply canister 38 through approximately ninetydegrees. Valve opener pin 56 pushes valve disk 52 into an open positionand reagent flows from reagent supply canister 38 into reagent holdingtank 36. After several seconds, reagent supply canister 38 empties, isremoved, and the cap is replaced. The empty reagent supply canister 38is returned to the fueling station.

In the event of ambient air below approximately −11° C., heater 58 maybe actuated to heat reagent within reagent holding tank 36. However,since reagent holding tank 36 is small it can also be attached to theheated cab sleeper and thus would not require electricity during thevehicle trip. However, if the vehicle is parked for an extended periodin the sub −11° C. weather, the urea solution could freeze and thereforea freeze tolerant tank design and a heater is required. In situationswhere the solution freezes during vehicle inactivity, the heating systemwithin reagent holding tank 36 is activated at the start of the truckengine. The heating system would be designed such that adequate ureasolution for operation would melt by the time the exhaust components(mainly catalyst) would reach the operating temperature.

If a reagent quality sensor 76 is used (e.g., an aqueous urea qualitysensor), the engine power can be reduced to a limp home mode if adequateurea solution is not available. This may be important since a lack ofadequate urea solution would result in tail pipe NOx emissions exceedingthe emissions standard. In addition, optional NOx sensor 78 can be usedto reduce engine power if any of the emissions control devices fail,such as an insufficient supply of urea in reagent holding tank 36

While this invention has been described as having a preferred design,the present invention can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

1. An internal combustion engine, comprising: an exhaust manifold; and aselective catalytic reduction exhaust aftertreatment system, including:a reduction catalytic converter in communication with said exhaustmanifold; a reagent holding tank in fluid communication with saidreduction catalytic converter; and a reagent supply canister selectivelyand removably couplable with said reagent holding tank.
 2. The internalcombustion engine of claim 1, wherein said reagent holding tank includesa refill head with a seal and a latch.
 3. The internal combustion engineof claim 2, wherein said seal comprises an O-ring seal.
 4. The internalcombustion engine of claim 2, wherein said reagent supply canisterincludes a nozzle with a spring biased valve and a mating latch.
 5. Theinternal combustion engine of claim 4, wherein said valve includes avalve disk biased by a compression spring.
 6. The internal combustionengine of claim 5, wherein said refill head includes a valve opener pinfor biasing said valve disk to an open position when said reagent supplycanister is coupled with said reagent holding tank.
 7. The internalcombustion engine of claim 4, wherein said latch comprises a bayonetlatch and said mating latch comprises a mating bayonet latch.
 8. Theinternal combustion engine of claim 1, wherein said reagent holding tankincludes a heater.
 9. The internal combustion engine of claim 8, whereinsaid heater includes at least one resistance heater.
 10. The internalcombustion engine of claim 1, wherein said reagent holding tank includesat least one reagent level sensor.
 11. The internal combustion engine ofclaim 10, further including a visual indicator coupled with at least onesaid reagent level sensor.
 12. The internal combustion engine of claim10, wherein said reagent holding tank includes two reagent levelsensors.
 13. The internal combustion engine of claim 1, wherein saidreagent holding tank includes a sump and a suction line having an inletin said sump.
 14. The internal combustion engine of claim 1, includingat least one of a reagent quality sensor and a NOx sensor.
 15. Theinternal combustion engine of claim 14, wherein said reagent qualitysensor is positioned in said reagent holding tank.
 16. An internalcombustion engine, comprising: an exhaust manifold; and a selectivecatalytic reduction exhaust aftertreatment system, including: areduction catalytic converter in communication with said exhaustmanifold; and a reagent holding tank in communication with saidreduction catalytic converter, said reagent holding tank including arefill head selectively couplable with a reagent supply canister, saidrefill head being substantially sealed with said reagent supply canisterwhen coupled with said reagent supply canister, and substantially sealedwith an ambient environment when not coupled with said reagent supplycanister.
 17. The internal combustion engine of claim 16, wherein saidrefill head includes a seal and a latch.
 18. The internal combustionengine of claim 17, wherein said seal comprises an O-ring seal.
 19. Theinternal combustion engine of claim 17, wherein said latch comprises abayonet latch.
 20. The internal combustion engine of claim 16, whereinsaid reagent holding tank includes a heater.
 21. The internal combustionengine of claim 20, wherein said heater includes at least one resistanceheater.
 22. The internal combustion engine of claim 16, wherein saidreagent holding tank includes at least one reagent level sensor.
 23. Theinternal combustion engine of claim 22, further including a visualindicator coupled with at least one said reagent level sensor.
 24. Theinternal combustion engine of claim 22, wherein said reagent holdingtank includes two reagent level sensors.
 25. The internal combustionengine of claim 16, wherein said reagent holding tank includes a sumpand a suction line having an inlet in said sump.
 26. The internalcombustion engine of claim 16, including at least one of a reagentquality sensor and a NOx sensor.
 27. The internal combustion engine ofclaim 26, wherein said reagent quality sensor is positioned in saidreagent holding tank.
 28. An exhaust aftertreatment system for aninternal combustion engine, comprising: a reduction catalytic converter;a reagent holding tank in communication with said reduction catalyticconverter; and a reagent supply canister selectively and removablycouplable with said reagent holding tank.
 29. The exhaust aftertreatmentsystem of claim 28, wherein said reagent holding tank includes a refillhead with a seal and a latch.
 30. The exhaust aftertreatment system ofclaim 29, wherein said seal comprises an O-ring seal.
 31. The exhaustaftertreatment system of claim 29, wherein said reagent supply canisterincludes a nozzle with a spring biased valve and a mating latch.
 32. Theexhaust aftertreatment system of claim 31, wherein said valve includes avalve disk biased by a compression spring.
 33. The exhaustaftertreatment system of claim 32, wherein said refill head includes avalve opener pin for biasing said valve disk to an open position whensaid reagent supply canister is coupled with said reagent holding tank.34. The exhaust aftertreatment system of claim 31, wherein said latchcomprises a bayonet latch and said mating latch comprises a matingbayonet latch.
 35. The exhaust aftertreatment system of claim 28,wherein said reagent holding tank includes a heater.
 36. The exhaustaftertreatment system of claim 35, wherein said heater includes at leastone resistance heater.
 37. The exhaust aftertreatment system of claim28, wherein said reagent holding tank includes at least one reagentlevel sensor.
 38. The exhaust aftertreatment system of claim 37, furtherincluding a visual indicator coupled with at least one said reagentlevel sensor.
 39. The exhaust aftertreatment system of claim 37, whereinsaid reagent holding tank includes two reagent level sensors.
 40. Theexhaust aftertreatment system of claim 28, wherein said reagent holdingtank includes a sump and a suction line having an inlet in said sump.41. The exhaust aftertreatment system of claim 28, including at leastone of a reagent quality sensor and a NOx sensor.
 42. The internalcombustion engine of claim 41, wherein said reagent quality sensor ispositioned in said reagent holding tank.
 43. A method of operating aninternal combustion engine, comprising the steps of: treating exhaustgas with a selective catalytic reduction system including a reductioncatalytic converter; supplying a reagent to said reduction catalyticconverter from a reagent holding tank; coupling a reagent supplycanister with a refill head on said reagent holding tank; and refillingsaid reagent holding tank with reagent from said reagent supplycanister.
 44. The method of operating an internal combustion engine ofclaim 43, including the step of removing said reagent supply canisterfrom said refill head.
 45. The method of operating an internalcombustion engine of claim 43, wherein said coupling step includessealing and latching said reagent supply canister with said reagentholding tank.
 46. The method of operating an internal combustion engineof claim 43, including the step of opening a valve in said reagentsupply canister, thereby allowing said refilling step.
 47. The method ofoperating an internal combustion engine of claim 46, wherein saidopening step occurs concurrently with said coupling step.